Lymph is formed from the interstitial fluid found throughout tissue and is similar in composition to blood plasma, lacking red blood cells. The lymphatic system plays a role in circulating blood back to the heart as well as passing it though the lymph nodes to clear it of any infectious agents.
Tissue fluid is found between cells and its role is to transport oxygen and nutrients from blood to cells, and waste products and carbon dioxide back to blood. It is similar to blood plasma, lacking blood cells and proteins.
Hydrostatic pressure determines the flow of these fluids between the different systems in a tissue. The oxygenated blood travelling through capillaries from arterioles has a high hydrostatic pressure, pushing the liquid outwards through small pores. This contains all the nutrients and gases cells need, which cross plasma membranes via diffusion or facilitated diffusion. Big components of blood such as cells and plasma proteins cannot escape the capillary, so stay in the blood.
The tissue fluid is then collected back via a water potential difference between itself and blood. Water moves by osmosis back into the blood in capillaries due to blood having more solutes and hence a lower water potential. This is a special subtype of osmosis called oncotic pressure and is derived from the presence of proteins such as albumin in blood that has the effect of pulling water into the capillary.
Some tissue fluid, such as excess tissue fluid, doesn’t return to blood and instead is drained into the lymphatic system. This forms lymph which is poorer in oxygen and nutrients, and returns to blood later on.
Thank you for the help, your website and videos are awesome
pika mart YouTube
I’ve struggled so much with feeling overwhelmed with biology revision, and I don’t know where to start. But your website is just what I need! It tells me all the information I need, and the knowledge I need to then build on, and it’s written in a way that soaks straight up into my brain!
Prettyhetty The Student Room
Thank you for making all the content btw!
Serena Kutty YouTube
Hi! I have recently finished my first year doing biology at uni and I subscribed to you back when I was doing AQA A levels (glad I don’t live in Wales after watching this vid lol) and you and your website helped me so much. Just wanted to say it’s so nice to see you
Mr Peanutbutter YouTube
You explain everything so simply!
SecretDuck The Student Room